For annoyingly fine-pitched devices I prefer the thinnest solder possible. Like the .4mm or .5mm stuff....let's go with 0.5mm for now as there are more choices at your site.
I don't particularly think you need a low-melting-point solder for general applications so you can do away with the more expensive choices, and go with the Stannol 518639 or Multicore 442560 (Halide-free so a little less active but nicer for the environment and less residue).
Just my 0.02p
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons